This invention relates to a numerical control (NC) programming apparatus. More particularly, the invention relates to an NC programming apparatus used in creating an NC program for machining a workpiece in separate quadrants by each of a plurality of tools, or in verifying an already created NC tape in which the NC program has been punched.
A lathe having four simultaneously controllable axes, referred to hereinafter simply as a "four-axis lathe", is equipped with two tool rests each of which is independently controlled during the machining of a workpiece. Such a lathe may come equipped with one or two spindles. FIG. 1 is an explanatory view of a four-axis lathe having one spindle. The reference symbol SP represents the spindle, WK a workpiece held and rotated by a chuck CHK, and TL1, TL2 first and second tool rests, respectively. With a four-axis lathe of this kind, the two tool rests TL1, TL2 respectively machine the single workpiece WK in the first and fourth quandrants of the XZ plane, where the x axis is the axis by the spindle, enabling machining efficiency to be greatly improved.
Since the tool rests TL1, TL2 are transported in the first and fourth quadrants, respectively, an NC program is created for moving the tool rest TL1 in the first quadrant, and another NC program is created for moving the tool rest TL2 in the fourth quadrant. It has been attempted to display or plot the path of each tool on a CRT or plotter as the NC programs are being created, or in accordance with an already created NC tape in which the NC program have been punched. Since the machining is carried out in separate quadrants, one tool path is displayed or plotted in the first quadrant and the other in the fourth quadrant, as illustrated in FIG. 2. (It should be noted that the dashed line in FIG. 2 is not displayed or plotted.) This makes it difficult to grasp the overall contour machined by the tools of the tool rests TL1, TL2, and it cannot be readily ascertained whether the NC programming is correct. In other words, with an automatic programming apparatus in which a workpiece is machined in separate quadrants by each of a plurality of tools, a problem confronted in the prior art is that the paths traversed by the tools cannot be displayed together in one and the same quadrant, making it difficult to correctly apprehend or perceive the final, overall shape and, hence, to check the programs.